Asteroid Impact Effects

[martianant]

I'd like to suggest a slight change:
Whole asteroid -> world destroyed
large chunk -> world transformed into lava world
small chunk -> city/life wipe

Inspired by real life, a simulation of a 500km asteroid hitting earth.

But as stated in the video you linked. This has possibly happened to the Earth 6 times, and Earth isn't a "lava world".
Sure right after the impact the Earth was likely a firey hellscape for a while, but it didn't stay like that.
And some asteroid impacts might instead result in an impact winter, but that would also be temporary.

I agree that it would be cool if the world was uninhabitable for a while after an impact, with nice visual effects and such, but it should be temporary. It could require you to use buildings with harsh environment protection on the world while the effect is active. Could even make it so that the smaller impacts only destroy buildings that don't have adequate harsh environment protection. Then when the effect wears off, maybe after a week or two, the world returns to normal but with new/changed animal and plant life.

That is an asteroid that is 500km, compared to the earth's diameter of 12756km. In the video, the large chunks look very very large, and scale wise would not be "500km" but much much larger, probably on scale with the body that hit the earth and formed the moon. Here is a little video of that impact.
We must also consider time. Yes, your point is more for the small chunks, which is what that video represents. The large chunks is more for the second video. I apologize, I should've made more clear. Although even with 500km, the oceans have boiled away and it's very inhospitable. But with a large chunk, it would stay molten for a significant amount of time, long enough that in gameplay terms it would be a "lava world."

Additionally, the change between planet destroyed, and planet changed to a lava world is in a sense better. If the player desired, they could build again using HEV building designs and biodomes. There are still great consequences for the player for not destroying the asteroid. And if they choose to restart, the world is left behind as a reminder to all the dangers of space.